Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 and TA1538 are being used to test chemicals of interest for mutagenicity. A series of cyclic hydrazides which are analogs of nitrosamines have been tested for mutagenicity for comparison with mutagenic and non-mutagenic nitrosamine counterparts. In addition Dimethylaminoazobenzene (Butter yellow) and two of its analogues, as well as 2,3,7,8-Tetrachloredibenzofuran and alkylnitrites will be tested.